From Analog to Software Defined:
A History of the Radio
Dr. Roland Kempter
[email protected]
1. The History of Radio Communication (incomplete)
2. Important Concepts: Filtering and Modulation
3. Background: Fourier Series Expansion
5. From Analog to Digital: Software Defined Radio
6. Programming Software Defined Radios
History of the Radio: James C. Maxwell
1861-1865: James Clerk Maxwell
experiments with electromagnetic
1873: describes the propagation of
electromagnetic waves in his paper
“A Dynamical Theory of the
Electromagnetic Field”
Wireless Radio Begins: Nikola Tesla
1893: Tesla gives public demonstration of
wireless radio communication
at St. Louis, Missouri.
He describes in detail the principles of radio
Wireless Radio Begins: Guglielmo Marconi and K. F. Braun
1896: G. Marconi is awarded a patent for radio:
Improvements in Transmitting Electrical
Impulses and Signals and in Apparatus
1897: Marconi establishes a radio station
on the Isle of Wight (England)
1909: Marconi and Karl Ferdinand Braun win
Nobel Prize in Physics for
"contributions to the development of
wireless telegraphy"
The History of the Radio
Better Sound Quality: FM Radio
1933: Edwin H. Armstrong patents FM radio
(better quality than AM)
1940s: analog television transmissions start
in North America and Europe.
The History of the Radio: the 21st century
Internet radio
Streaming Internet connection, no RF, IF, etc.
Digital Audio Broadcasting (DAB)
alternative to FM
Satellite Radio
XM Radio, Sirius Satellite Radio
Going from analog “payload” to digital “payload”
However, radio itself still “analog” up
to the decoder stage
The Fundamental Blocks in a Radio
Increase amplitude of signal
multiply by constant
Move signal from RF to
baseband (original signal)
Remove frequency components
Fourier Series Expansion
The Theory Behind Radio Technology: Fourier Series
Jean Baptiste Joseph Fourier (1768-1830)
French mathematician and physicist
“any” periodic function can be decomposed
into an (infinite) sum of sines and cosines
Fourier applied it to to problems of heat flow.
1824: gases in the atmosphere increase
the surface temperature of the Earth.
Fourier described the greenhouse effect!
The Theory Behind Radio Technology: Fourier Series
Fourier Series
describes the frequency content of periodic signals
Different Time Domain signals have different
harmonics (# and magnitude)
Example: Square Pulse, infinite # harmonics!
With 250 harmonics:
Gibbs phenomenon
at discontinuity
Example: Sawtooth Wave
Example: Triangle Wave
Rect-wave: poor TD quality with 25 harmonics
Sawtooth-wave: poor TD quality with 25 harmonics
Triangle-wave: pretty good TD quality with 10 harmonics
Some TD signals are suited better for
transmission than others (less harmonics)
Example: Fourier Transform
(right) logarithm of the magnitude of the FT of Fourier
Courtesy of Thomas F. Weiss Massachusetts Institute of Technology
What is Modulation
Modulation: multiplication of baseband signal by a carrier wave
Periodic signal can be expanded into series of sine + cosine
 apply the above expression to every single one of those.
Move arbitrary baseband signal into higher bands
Fundamental Blocks: Why is Modulation Necessary?
At least 2 reasons:
1. different signals from different systems do not interfere
Example: - broad band cable services
- Public TV and Radio (wireless services)
2. move the payload signal to frequency where it can be
transmitted most easily
Problem: - signal attenuation in wires
- free space signal attenuation
What is Filtering?
Input Signal
Filter Response
Output Signal
Modulation and Demodulation
x fc
x fc
Fourier Series: Continuous and Discrete
Nice, but all of this was for continuous signals,
What about discrete (digital) samples?
Fourier works in digital, too: Discrete Fourier Transform
BPSK Radio
A Radio?
A Conventional Radio: all in Analog
New Paradigm: Software Defined Radio (SDR)
Software Defined Radio:
RX Signals are digitized immediately after the LNA
and then processed entirely in software, flexible
TX vice versa
A Radio!
SDR is Real!
23 November 2004:
FCC approves the first SDR device in the United States.
If radio changes behavior, no more re-approval necessary!
cellular base station:
HP proliant server,
ADC/DAC, running Linux,
can act as a GSM,
through software updates
Programming Software Defined Radios: Download?
Operator, I need a pilot program for a V-212 helicopter!
Different people have different brains!
Different Hardware, simple downloads won’t work!
Various manufacturers of SDR boards
 various flavors of hardware, on-the-fly reconfiguration
requires specific configuration files! Infeasible!
Describe to the target (brain) what to do:
Give presentations instead of .exe files
Programming Software Defined Radios: Now and Future
“Classical” way:
Problem: hardware (board) specific, rewrite for different boards
SCA, Software Communication Architecture
CORBA, XML with Object Request Broker (ORB) middleware
Ontology-based programming languages, “describe”
to the board what to do, board (compiler) figures out how
and if possible
1. Easier board programming, do it once for different architectures
2. Enable reconfiguration “on-the-fly”, download of new policies
SDR with Ontology Language
SDR to Operator:
I’ve been an AM radio all my life,
I want to become an FM radio!
You’ll need to reconfigure your demodulator.
How do I do that?
You need 15 multipliers and 20 adders,
do you have that?
Now connect….
About us: SDR at the Wireless Communications Lab
2 Laptops running the GNU radio software, modified to work as
4 by 4 MIMO system, progam PHY
In January:
upgrade to 3 boards that feature VIRTEX 4 + ARM 9 + DSP,
running real-time OS, program PHY, MAC and Network layers
Why all that?

From Analog to Software Defined: A History of the Radio